returns 承诺的循环库 - 同步

Question

我对这段代码摸不着头脑：我读取文件夹内容，通过 mammoth convert 循环接收文件（returns 一个承诺），然后我创建了一个我想要呈现的对象。我尝试过异步和承诺，但从未能够使其同步。能请教一下吗？

fs.readdir('Documents', function (err, files) {
    files.forEach(function (file) {      
      mammoth.convertToHtml({path: "Documents/"+file},options)
      .then(function(result){
          var html = result.value; // The generated HTML
          var messages = result.messages; // Any messages, such as warnings during conversion
          docContent.push({
            "skillName" : file,
            "skillData" : html
          })
      }).done()
   });
});

res.render("index",{docContent:docContent});

Answer 1

我也很难理解promise收集结果的概念^^;.
我认为记住 Promise.all() 可以收集 Promise 的结果是一个很好的起点。

请尝试以下。

    fs.readdir('Documents', function (err, files) {
        // convertingJob = [Promise, Promise,...]  
        const convertingJob = files.map(function(file) {  
            // just return promise and it will make above convertingJob array 
            return mammoth.convertToHtml({path: "Documents/"+file},options) 
                  .then(function(result){
                        var html = result.value; // The generated HTML
                        var messages = result.messages; // Any messages, such as warnings during conversion
                        // docContent.push({
                        //     "skillName" : file,
                        //     "skillData" : html
                        // })
                        return {
                            "skillName" : file,
                            "skillData" : html
                        }
                   })
                   // .done() // I'm not sure this is necessary
         });

         Promise.all(convertingJob) // Gather(wait) all Promise results!
         .then(jobResults => {      // jobResults would be array of objects returned by mammoth 
            res.render("index",{docContent:jobResults});
         })
    });

returns 承诺的循环库 - 同步

Looping library which returns a promise - sync

javascript

synchronization

asynchronous

node.js

promise